Means for preventing the accumulation of ice on aircraft surfaces and the like



y 1949- D. 1.. LOUGHBOROUGH 2,471,224

MEANS FOR PREVENTING THE ACCUMULATION 0F ICE ON AIRCRAFT SURFACES AND THE LIKE Filed April 19, 1945 Humble 2 Esau/$0M "3 v Patented May 24, 1949 UNITED TATES PATENT MEANS =FORPR-EVENTING THE AceUMUI-h TION F ICE 0N AIRCRAFT JSURFACES ANDTHE LIKE Dwight L. .Lou'g hb'o'rough, Akron, Qhie, ass gn t .The B- F. Good Ge many, New 102k "N; a corporation of New York Application April .19, 1945, Serial 1N0. 589,124

k 20 Claims.

This vinve'ntien lg elates to means -fqr prevent- ;ing the accumulation 0f lee .on {surfaces and vis especially useful "for brbtecting against the haecumulation of dangerous quantities efiice-onthe leading edges of .airfoils and other portibns of airbraftinfiight.

Wintehand high altitude flying involves a seiious hazard ,ies'ul'tii'lg ,frofn accumulation "of t e -eh menacing .ejdges Of aircraft wings, control fsurfaeesetruts, prqpeller'sandithe like, This ,.hazard has beenenmbIatted ,With -bnsid'erahle nen ss by hovenin the leading edges "of airfei-ls with a flexible Sheath, preferably bf \el'astie rubmy mateitial, and periodica .distbrting me 'sheathji ring flight to change its shape and. break lojdseany jibe which may have, accumulated .tlleliepn so that, theiee maybe swept away by the air stream. In the cpmmereial fqrm fof this jigleir ice so1d unjde1" -the trade-mark ,De-Icer, tl'istorft'i on "of the rubber sheath ,is effected by alt nately inflatin .sfets or inflatable. tubes tund iv g the she th use as to effect .s't e n and shifting of the exposedsurfac e fthfe sheath. .It has also been prpos'ed to effect such distention of the sheathfby varipus me'elrl'arliea1 means inbinding rqtating cams,flevei'tmechanisms reciproeating arms, travelling rollers (and the like. Flexible rubber vanes jh'ave been mounted on struts for flexing in the Wind stream and so breaking loose iqe .fermed there'Qn. Similarly, rhbhe'y discs and sheaths 'h'avebeenemqunted Qn prbpeller'sto eOYnbat ice formation.

I have found that the effectiveness .o'f such devices in -pr6te cting against ice accumulation may be greatly enhanced by providing a.surf'ace 0'1" fil'xn ,cbatir g of silicone material at the surface eh-posed to'ieing conditions. The adhesive bond between the rubberysllrthce and :the ice m'ay thereby 'be 'redueed by as much as "90% Q1 mole with {the result that ;ice removal in the vair stream aha uhc'l'ef the breaking influence of periqdic surface distbrtiens is greatly facilitated.

The -silicone *i'nater ia-l-s' iieferahly employed .in the invention are the fer'gano siliebh {polymers derived fi on'ierganbj-siliee'n halides and may "be mdheed in situ by treeehg the rubbery surface 6f the iee-er'erneval ail-spasms with an apprqpriate orgahosilicqn halide whereupdmo mh n ,of-the si1ieon'e dc'cursspbntanously,'01 the silicone they he resprepereq in zmi bf a Variety of physiea'l iidrins *a-Pplieil essueht6 the rubbery surface. It is also Q'ssihie tePiheOrbQrate 'the silie 'ne metehm iirtbth'e 'gubbei y eomposition *from wh ch the flexible sheath is prod ced, ,or even to -formthesheath itself frqi'n certainfitypes of .efqrmjstincludingliguidspf varying yiscositl.

silieones. ,Although so m,,e vahiatipn ;has ;heen noted in the efiegtivenes'ssof these ya ipus modes of :aQPli-eation, .-al1 xpf ;them .-are effectitze ,te i educe .ice adhesion-to {a -\small :fraction of its nor"- al e .v v

T he silicones utiliz ed in the inventiqh Well as the woz gano sihc n halides rorn whieh they .are preferalolgs derived, hephtaih efi v"i "om the ,QQweQQifni g .Co r ndhetiqnland fiqm EIhegGeneifal ,Eleetrictcom any. These iiiateigialsahedescribed .in -L\ za ri'c i1s ;1i,flei'atu1je neles in luding athe Corning Glass WQE1$ @BntishPajtent :NQ, 551,136, Qhe'rh c'el and tM tll'ureiel. .,Efrleineelq.ifig Au ust, 1,944,.atpeee 1'oe, a st anid 1.36, fiGe er'al tileeth neview fdhhugu'st, 494A, Mqqern .Elastic's .-f.0i' NQimhQr 194%,; thetartiele he'- .fginning 'at pa e 1214 entitled v Redne s-High ,Polymeiiic substahfi fi? and iqhfem l al find "Env ineering .New's ,,fd1*;Nvember 119M, -at pa e 21116.

The silicone-s exist in a jet.iiajiy 6f ph sieal 011$, greases, and mote (Q'r less resilient :ahd elastic solids or elastomeiis which may be .geompourhlefi and vulcerfi'zedzt'o jo'btain Ia p'lnc'x 'll'ct resemblin yuleanized rubheiin many respeets. "jlhejse various types as well as hard iesinousifidrmspf silicones which maybe pl'astieized all .Qaiie useful 'inthe firesent'ini en ti'n.

The si1icdnes,' 6r silbxan'es as 'they ai"e-,semetimes called, are derived frqm prg'anq-fsi ebn halides Lby .proe'esfi Lmfdrs ddstbjnvqlye 11ydrdlysis 'of the "halide fdllowed by pQl'yinefimtihn of the sultih j ilahql f(oi't,silicdl) It appears that sumeiem moisture s .tllnifinah i'esent at the surface of arubbei' p'ijdduct or in the s rrounding atmosphere to permit qtmation qf the silicone tq p'c'cu r spentaneeysl" injcegit hasbeen observed that treatmeht 0i .1; e rubbeigyshfiaee pf ice removal apparatus w1t -,-r orexemp1s, vapqrous 0,17 "liquid dimethyl =silildh ,diChlQrifle rfes its in the"'f'or'me io f i atenacioush'r idhered ffilm gqver the treated surface. "Thefilmijs quite xfljexible and tan be stretched repeatedly without breaking so that it is p culiarly adaptedjfor use .on inflata le ice i'lemoving devices.

m ng the br ehoes liceh hal des .u'sei'lll in th invention are the alkyl 'silieon halides, 'thearyh silicon halides a d h mixed .-al1 yl-;ars?1'-;si1i 0n alide ncluding but .not i'beih'g l mite ltmth xemp arymate iels .diin Z ride, dibenzyl silicon dichloride, dichlorophenyl silicon dichloride, ethyl silicon tribromide, methyl phenyl silicon dibromide, and many others such as are described in the above-mentioned literature references, as well as mixtures of the above with the same or other silicon halides.

Outstanding results have been obtained by treating rubbery surfaces with dimethyl silicon dichloride either alone or in admixture with other similar organo-silicon halides. For example, a mixture understood to contain a minor propor tion of monomethyl silicon trichloride and a major proportion of dimethyl silicon dichloride together with a very minor proportion of trimethyl silicon chloride has been used with success.

These organo-silicon halides may be applied to the surfaces to be treated in any manner desired, such as by applying in vapor form, in liquid form or in solution. Excellent results have been obtained by treating a rubbery surface directly with vaporous or liquid dimethyl silicon dichloride. It may be preferred, however, as a practical matter and for economy of application, to apply the materials in the form of solutions of the organesilicon halides dissolved in volatile solvents. Suitable solvents include hydrocarbons, esters, alcohols, ketones or the like. For best results, it is preferred that hydrocarbon or halogen-substituted hydrocarbon solvents be employed. These latter solvents include benzene, naphtha, carbon tetrachloride and many others of a similar nature.

In a typical example, a 50% solution, by weight, of dimethyl silicon dichloride in benzene was prepared. This solution was brushed onto the surface of a rubber ice removal device of the type sold under the trade-mark De-Icer and the solvent was permitted to evaporate, whereupon a tenaciously adherent flexible and stretchable film was produced on the rubber as hereinabove described. Ice was formed on this surface by subjecting it to icing conditions. The adhesion of the ice was only 6.7 lbs/sq. in. When a similar rubber surface was subjected to the same icing conditions but without the surface having been treated as set out above, the adhesion of the ice was found to be 67.5 lbs/sq. in. showing that treatment of the surface with the dimethyl silicon dichloride reduced the adhesion of the ice by about 90%.

As has been indicated, it is also possible to preprepare the silicones from suitable initial materials such as the organo-silicon halides hereinabove set out, and to apply the polymeric silicone material to the rubbery surface in liquid, solid or solution form. Also, the silicones may be admixed with the rubbery material itself.

If a liquid polymeric silicone is to be used, the liquid may be applied directly to the surface of the rubbery sheath or it may be compounded into the rubbery composition from which the sheath is made, preferably in an amount of from 1% to based on the weight of the rubbery material. For direct application to the sheath, the liquid may be diluted with one of the solvents hereinabove mentioned if desired, although this is not necessary and the liquid silicone may be applied without dilution.

In a further example of the invention, a liquid polymeric silicone was prepared from a mixture of dimethyl silicon dichloride and monomethyl silicon trichloride containing traces of trimethyl silicon chloride. The liquid silicone, which had an initial boiling point of around 165 C., was applied directly to the surface of the inflatable element of an ice removal apparatus made from vulcanized neoprene. The silicone formed a tough film over the surface, the film being freely elastic and extensible so that it did not break when the rubbery material was stretched upon inflation of the apparatus. When the treated surface was subjected to icing conditions, the resulting ice was found to have an adhesion of only about 11 lbs/sq. in. as compared to an adhesion of '75 lbs/sq. in. on an untreated surface of the same kind.

The greasy types of silicone polymers may be smeared over the rubbery surface to provide effective reduction in ice adhesion. Thus, an inflatable ice remover made of vulcanized neoprene was thinly coated by a hand-spreading operation with the sticky, greasy silicone polymer designated commercially as Dow Elastomer. Adhesion of ice to the treated surface was thereby reduced to about 2.5 lbs/sq. in. as compared with a normal adhesion in the neighborhood of '70 lbs/sq. in. Such a coating also may be applied by first dissolving the silicone grease in a suitable solvent such as benzene.

Similar tests show that adhesion of ice to a surface of the elastic and resilient silicone polymer designated by The General Electric Company as Silicone Rubber is less than 10 lbs/sq. in. A preformed fllm or sheet of such silicone rubber may be adhered or mechanically secured over the rubbery surface of an ice removal apparatus or the silicone rubber may be dissolved in a solvent and applied as a cement coating which upon drying will deposit a film of silicone rubber. Also, the protective sheath itself may be formed entirely of such material by known methods although fabric reinforcements and a rubbery backing generally will be desirable. Like the liquid polymers, the rubbery polymers also may be admixed with natural or synthetic rubbery materials of the character presently used in fabricating ice removing apparatus, all with advantageous effect in reducing adhesion of ice to the surface of products made therefrom.

In utilizing solutions of the various silicones for treating rubber, it will in many cases be found advantageous to include natural or synthetic rubber in the cement solution.

The accompanying drawings illustrate typical applications of the present invention in preventing the accumulation of ice on aircraft surfaces.

Of the drawings:

Fig. 1 is a conventionalized fragmentary perspective view of an aircraft with apparatus for preventing the accumulation of ice in accordance with the present invention mounted on the leading edges of the wings.

Fig. 2 is a sectional perspective view taken along the line 2-2 of Fig. 1 and showing more specifically details of an inflatable type of ice removing apparatus mounted on the aircraft wing.

Fig. 3 is a fragmentary sectional perspective view illustrating a modified type of device for preventing the accumulation of ice on aircraft parts and also embodying the present invention.

Referring to the drawings, the numeral l0 designates a conventional aircraft having inflatable boots II, II of the De-Icer type mounted on the leading edges of the wings. For simplicity of illustration, a simplified form of boot has been shown consisting of a rubbery sheath I 2 mounted in stretched condition over the leading edge of the wing I3 with the margins of the sheath being secured to the wing by fairing strips l4 suitably riveted or otherwise attached to the leading edge of an airfoil exposed to icing condi- 10 tions for preventing accumulation of ice thereon, said apparatus comprising an inflatable boot having an exposed surface formed of flexible elastic rubbery material which has been surface treated with an organo-silicon halide, said treated surface being resistant to the adhesion of ice under said icing conditions.

12. Ice-removing apparatus comprising an expansible member formed of flexible elastic rubbery material, means for expanding said member to break ice therefrom, and means on an exposed surface of said member for reducing adhesion of ice thereto, the last said means comprising a flexible elastic film of polymeric silicone material produced by treating said surface with an organo-g silicon halide.

13. The method of reducing the adhesion of ice to a rubbery surface of an aircraft ice-removing boot normally subjected to icing conditions which comprises applying to the said rubbery surfacev an organo-silicon halide, providing thereby a resulting extensible elastic film on said surface stretchable With the rubbery material and resistant to adhesion of ice under said icing conditions.

14. The method of reducing the adhesion of ice to a rubbery surface of an aircraft ice-removing boot normally subjected to icing conditions which comprises coating said rubbery surface with a silicone, providing thereby a resulting extensible elastic film on said surface stretchable with the" rubbery material and resistant to adhesion of ice under said icing conditions.

15. The method of reducin the adhesion of ice, to the surface of an aircraft ice-removing boot of a rubbeiy material normally subjected to icing conditions which comprises applying to the said' surface a solution of an organo-silicon halide in a volatile solvent, and thereafter permitting the solvent to evaporate, providing thereby a result-' ing extensible elastic film on said surface stretchable with the rubbery material and resistant to adhesion of ice under said icing conditions.

16. The method of reducing the adhesion of ice to the surface of an aircraft ice-removing boot of rubbery material normally subjected to icing conditions which comprises applying to the said surface a solution of an organo-silicon halide in a volatile solvent selected from the class consisting of hydrocarbons and halogen-substituted hydrocarbons, and thereafter permitting the solvent to evaporate, providing thereby a resulting extensible elastic film on said surface stretchable with the rubbery material and resistant to adhesion of ice under said icing conditions.

17. The method of reducing the adhesion of ice to the surface of an aircraft ice-removing boot of a rubbery material normally subjected to icing conditions which comprises treating said rubbery surface with dimethyl silicon dichloride, providing thereby a resulting extensible elastic film on said surface stretchable with the rubbery material and resistant to adhesion of ice under said icing conditions.

18. The method of reducing the adhesion of ice to the surface of an aircraft ice-removing boot of a rubbery material normally subjected to icing conditions which comprises applying to said rubbery surface a solution comprising dimethyl silicon dichloride in a volatile solvent, and thereafter permitting the solvent to evaporate, providing thereby a resulting extensible elastic film on said surface stretchable with the rubbery material and resistant to adhesion of ice under said icing conditions.

19. The method of treating a rubber ice-removing device for an aircraft to lower the adhesion of ice thereto which comprises applying an organo-silicon halide to an exposed rubber surface of said device, providing thereby a resulting extensible elastic film on said surface stretchable with the rubbery material and resistant to adhesion of ice under said icing conditions.

. 20. Apparatus adapted to be associated with an aircraft surface exposed to icing conditions for preventin accumulation of ice thereon, said apparatus comprising a flexible elastic distortable element formed of rubbery material arranged to be mounted on said surface, an exposed surface of said flexible element comprising a silicone resistant to the adhesion of ice under said icing conditions.

DWIGHT L: LOUGI-IBOROUGH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,890,286 Geer Dec. 6, 1932 1,998,809 Geer Apr. 23, 1935 2,258,218 Rochow Oct. 7, 1941 2,306,222 Patnode Dec. 22, 1942 2,327,034 Geer Aug. 1'7, 1943 2,439,689 Hyde Apr. 13, 1948 2,441,098 Hyde May 4, 1948 

